Various types of joints exist for connecting a compressor wheel to a shaft. Some joints rely on a bore in the compressor wheel along the axis of rotation. In such joints, a shaft passes through the bore and a nut secures the wheel to the shaft. Other joints rely on a “boreless” compressor wheel. A boreless compressor wheel includes a joint or chamber that extends a distance into the compressor wheel where the distance along the rotational axis typically does not extend to or beyond the z-plane of the compressor wheel.
In either instance, the bore or joint must be formed or machined into the compressor wheel. Stresses introduced by such processes may compromise wheel integrity such that a wheel fails during operation. Yet further, if one chooses to use titanium or other hard material for a compressor wheel, machining of a joint can be time and resource intensive.
Another concern pertains to balancing a compressor wheel. Boreless compressor wheels pose unique challenges for balancing. Compressor wheels may be component balanced using a balancing spindle and/or assembly balanced using a compressor or turbocharger shaft. Each approach has certain advantages, for example, component balancing allows for rejection of a compressor wheel prior to further compressor or turbocharger assembly; whereas, assembly balancing can result in a better performing compressor wheel and shaft assembly.
For conventional boreless compressor wheels, balancing limitations arise due to aspects of the boreless design. In particular, conventional boreless compressor wheels require shallow shaft attachment joints (e.g., typically not extending to or beyond the z-plane) to minimize operational stress. Such shallow joints can introduce severe manufacturing constraints. To overcome such constraints and/or other issues, a need exists for a new compressor wheel joint. Accordingly, various exemplary joints, compressor wheels, balancing spindles, assemblies and methods are presented herein that aim to meet aforementioned needs and/or other needs.